Methods, baseband unit system, aggregation unit and radio unit of a distributed base station system for handling uplink communication

A method performed by a first aggregation unit, AU, of a distributed base station system, the distributed base station system further comprising a first RU comprising N1 antennas, the first RU being connected to the first AU via a first AU fronthaul, FH, link and a second RU comprising N2 antennas, the second RU being connected to the first AU via a second AU FH link, the distributed base station system further comprising a baseband unit, BBU, connected to the first AU over a first BBU FH link, the method comprising:

• receiving, from the first RU over the first AU FH link, at least a part of first intermediate BFW C1 determined to be used for centralized interference mitigation based on a first UL channel estimate Ĥ1 of a communication channel between a first number of UEs and the first RU;
• receiving, from the second RU over the second AU FH link, at least a part of second intermediate BFW C2 determined to be used for centralized interference mitigation based on a second UL channel estimate Ĥ2 of a communication channel between a second number of UEs and the second RU;
• combining the at least part of first intermediate BFW C1 with the at least part of second intermediate BFW C2 into combined intermediate BFW Ccom;
• sending, to the BBU over the first BBU FH link, the combined intermediate BFW Ccom;
• and one of:
• receiving, from the first RU, intermediately-beamformed UL data streams of first user layers K1 originating from the first number of UEs intermediately beamformed based on first part of BFW for the first RU WRU1 obtained based on the first UL channel estimate Ĥ1, receiving, from the second RU, intermediately-beamformed UL data streams of second user layers K2 originating from the second number of UEs, intermediately beamformed based on first part of BFW for the second RU WRU2 obtained based on the second UL channel estimate Ĥ2, combining the received intermediately-beamformed UL data streams of the first user layers originating from the first RU with the received intermediately-beamformed UL data streams of the second user layers originating from the second RU, and sending the combined intermediately-beamformed UL data streams to the BBU, and
• receiving, from the BBU, at least a portion of a second part of BFW WBBU determined based on an inverse calculation of at least the combined intermediate BFW Ccom, sending, to the first RU, at least a first RU-adapted portion of the second part of BFW WBBU,1, sending, to the second RU, at least a second RU-adapted portion of the second part of BFW WBBU,2, receiving, from the first RU, completely beamformed UL data streams of the first user layers, beamformed based on final BFW for the first RU determined based on the first part of BFW for the first RU WRU1 and the first RU-adapted second part of BFW WBBU,1, receiving, from the second RU, completely beamformed UL data streams of the second user layers, beamformed based on final BFW for the second RU determined based on the first part of BFW for the second RU WRU2 and the second RU-adapted second part of BFW WBBU,2, combining the completely beamformed UL data streams of the first user layers received from the first RU with the completely beamformed UL data streams of the second user layers received from the second RU, and sending the combined completely beamformed UL data streams to the BBU.

A method performed by a baseband unit, BBU, system of a wireless communication system, the wireless communication system comprising a distributed base station system, the distributed base station system comprising a BBU, a first aggregation unit, AU, connected to the BBU over a first BBU FH link, a first RU comprising N1 antennas, the first RU being connected to the first AU via a first AU FH link, and a second RU comprising N2 antennas, the second RU being connected to the first AU via a second AU FH link, the method comprising:

• receiving, from the first AU, combined intermediate BFW Ccom comprising at least part of first intermediate BFW C1 combined with at least part of second intermediate BFW C2, the at least part of first intermediate BFW C1 originating from the first RU and being determined to be used for centralized interference mitigation based on a first UL channel estimate Ĥ1 of a communication channel between a first number of UEs and the first RU, the at least part of second intermediate BFW C2 originating from the second RU and being determined to be used for centralized interference mitigation based on a second UL channel estimate Ĥ2 of a communication channel between a second number of UEs and the second RU;
• determining second part of BFW WBBU based on an inverse calculation of at least the received combined intermediate BFW Ccom;
• and one of:
• receiving, from the first AU, combined intermediately-beamformed UL data streams, combined of intermediately-beamformed UL data streams of first user layers K1 originating from the first number of UEs, intermediately beamformed by the first RU based on first part of BFW for the first RU WRU1 obtained based on the first UL channel estimate Ĥ1, and of intermediately-beamformed UL data streams of second user layers K2 originating from the second number of UEs, intermediately beamformed by the second RU based on first part of BFW for the second RU WRU2 obtained based on the second UL channel estimate Ĥ2, and beamforming the received combined intermediately-beamformed UL data streams based on the determined second part of BFW WBBU, and
• sending, to the first AU at least a portion of the second part of BFW WBBU, and receiving, from the first AU, combined completely beamformed UL data streams combined from completely beamformed UL data streams of the first user layers beamformed based on final BFW for the first RU determined based on a first part of BFW for the first RU WRU1 and a first RU-adapted portion of the second part of BFW WBBU,1 and from completely beamformed UL data streams of the second user layers beamformed based on final BFW for the second RU determined based on a first part of BFW for the second RU WRU2 and a second RU-adapted portion of the second part of BFW WBBU,2.

A first aggregation unit, AU, configured to operate in a distributed base station system, the distributed base station system further comprising a first RU comprising N1 antennas, the first RU being connected to the first AU via a first AU fronthaul, FH, link and a second RU comprising N2 antennas, the second RU being connected to the first AU via a second AU FH link, the distributed base station system further comprising a baseband unit, BBU, connected to the first AU over a first BBU FH link, the first AU comprising a processing circuitry and a memory, said memory containing instructions executable by said processing circuitry, whereby the first AU is operative for:

• receiving, from the first RU over the first AU FH link, at least a part of first intermediate BFW C1 determined to be used for centralized interference mitigation based on a first UL channel estimate Ĥ1 of a communication channel between a first number of UEs and the first RU;
• receiving, from the second RU over the second AU FH link, at least a part of second intermediate BFW C2 determined to be used for centralized interference mitigation based on a second UL channel estimate Ĥ2 of a communication channel between a second number of UEs and the second RU;
• combining the at least part of first intermediate BFW C1 with the at least part of second intermediate BFW C2 into combined intermediate BFW Ccom;
• sending, to the BBU over the first BBU FH link, the combined intermediate BFW Ccom;
• receiving, from the first RU, intermediately-beamformed UL data streams of first user layers K1 originating from the first number of UEs, intermediately beamformed based on first part of BFW for the first RU WRU1 obtained based on the first UL channel estimate Ĥ1, receiving, from the second RU, intermediately-beamformed UL data streams of second user layers K2 originating from the second number of UEs, intermediately beamformed based on first part of BFW for the second RU WRU2 obtained based on the second UL channel estimate Ĥ2, combining the received intermediately-beamformed UL data streams of the first user layers originating from the first RU with the received intermediately-beamformed UL data streams of the second user layers originating from the second RU, sending the combined intermediately-beamformed UL data streams to the BBU, or
• receiving, from the BBU, at least a portion of a second part of BFW WBBU determined based on an inverse calculation of at least the combined intermediate BFW Ccom, sending, to the first RU, at least a first RU-adapted portion of the second part of BFW WBBU,1, sending, to the second RU, at least a second RU-adapted portion of the second part of BFW WBBU,2, receiving, from the first RU, completely beamformed UL data streams of the first user layers, beamformed based on final BFW for the first RU determined based on the first part of BFW for the first RU WRU1 and the first RU-adapted second part of BFW WBBU,1, receiving, from the second RU, completely beamformed UL data streams of the second user layers, beamformed based on final BFW for the second RU determined based on the first part of BFW for the second RU WRU2 and the second RU-adapted second part of BFW WBBU,2, combining the completely beamformed UL data streams of the first user layers received from the first RU with the completely beamformed UL data streams of the second user layers received from the second RU, sending the combined completely beamformed UL data streams to the BBU.